First things first I would like to say that this strategy doesn't work very often when attacking bases that are town hall level 9 and town hall level 10 due to the amount of air defenses and the level of most of their air defenses. I can assure you that by using this guide to attack any base that is TH8 or lower with a dragon-based deployment, you will succeed in 3 starring your opponent. There are a series of steps you should follow when doing so and I am about to reveal those to you.
1. Looking for a good base to attack.
Now, as a high level town hall 8, my way of choosing bases in war may be different than a town hall 7 would be. For instance, the bases that I choose are usually high level town hall 8s as well with very good base designs. This may not be the same for you guys, but I will try to explain every circumstance. Most bases that are town hall 6 or lower will be destroyed easily by dragon-based armies (when I say dragon-based armies, I usually mean an army with 6 or more dragons in it). Most lower-level town hall 7 bases will also be destroyed fairly easily by dragon-based armies (depending on the setup of the base and the setup of the attack). Now, for high level town hall 7 bases, choosing the base depends almost solely on the placement of the air defenses (which i will refer to as "ADs"). Almost all TH7 bases with at least one AD on the outside will be fairly easy to take out, so look for those, especially if that base has low-level ADs. Now, for TH8 bases, I suggest being a lot more careful when picking your bases. The best ones to attack will be bases with low-level ADs and/or bases with their ADs on the outside. It seems like it should be easy, but you will come to a point in which all of the available bases will meet any of these requirements. Later I will explain how to deal with this kind of situation.
2. How to build the right army for the base you're trying to attack (assuming you have 200 housing spaces).
-TH6 or lower
-6+ dragons and any other troop should be more than enough.
-TH7 with ADs on the outside -or- TH7 with low level ADs (level 2 or lower)
-6+ dragons and other troops that would be beneficial to the battle (suggested troops would be archers,
wizards, or hogs), also be prepared to arm yourself with 3 lightning spells in case something goes wrong.
-TH7 with centralized ADs and/or high level ADs
-8-9 dragons armed with archers or wizards, 3 lightning spells (preferably level 3+), and maybe a barb king.
-TH8 with ADs on outside and/or low level ADs
-8-9 dragons armed with either a group of 4+ hogs, or archers/wizards; 3 lightning spells, and maybe a barb
-TH8 with centralized ADs and/or high level ADs
-9 dragons armed with 20 archers, 3 higher level lightning spells, and preferably a barb king
3. How to attack.
-TH6 or lower
-There really aren't many requirements for this type of attack. For a quicker/smoother win, try to place your dragons close to the AD. Also, NEVER place all of your dragons in one bunch! Clan castle troops will have a field day with a group of bunched up dragons and can end your attack in seconds. This rule stands for ALL attacks using dragons regardless of the base.
-TH7 with ADs on the outside and/or low-level ADs
-This is a type of attack in which you can get pretty versatile with. If the ADs are on the outside, I would try to use a minimum of 4 hogs to take it out right away so that you don't have to deal with it right away. If you do this and also want to use 3 lightning spells to take out the second AD, feel free. This way you can attack without any ADs at all, which I believe even 4-5 dragons could 3 star with ease. But if you do not have the lightning spells or do not want to use them, I suggest placing your dragons in a position that would make it easier for the dragons to take out that last AD quickly so that the rest of your dragons can destroy the rest of the base with ease. Now, if the ADs are centralized, but they are lower level, I suggest using 7+ dragons and the rest archers. Choose a side of the base in which you want to place your dragons in order to get to the ADs as fast as possible (try not to split them in half, that won't help). Most people can do this, but they don't know the real secret to controlling the movements of the dragons without the AI killing your attack. The trick is to pick a side and place half of your archers on each adjacent side of where you want to attack, but closer to the side that you want to attack. This way, the dragons will go towards the middle and will not attack around the outside. Also, if possible, use 3 lightning spells and destroy the AD furthest away from you. In this case, try not to worry about the clan castle troops if the clan castle is in the middle (in which it often is), because they can often be helpful in your attack by luring the dragons closer to the middle and thus closer to the ADs and the coveted town hall of your opponent's base. if you have a barbarian king, try to save him until the middle of the attack and place him in the place in which he can do the most damage.
-TH7 with centralized and high level ADs
-With this attack you have to be careful. The army that I use for these is 9 dragons, 20 archers, and 3 lightnings spells (plus my barb king and clan castle troops which are optional). First thing you will do is choose a side of the base to attack and get to ONE of the ADs very quickly. Use your 3 lightning spells to destroy the other AD. Next, place half your archers on each adjacent side of the side in which you want to attack, with your main goal to take out the corners of the opponent's base so that your dragons don't get distracted and start attacking the outside of the base. That would be disastrous, so we have the archers direct the dragons inside the base and wreak havoc that way. If you have a dragon in your clan castle, which is preferable, I would suggest waiting to place it later in case the dragons steer away from the objective. Use this dragon to destroy anything that would get the rest of the dragons back in the right direction or help those other dragons survive. Then if you have a barbarian king, place it somewhere that it will do the most damage and destroy the most buildings.
-TH8 with ADs on the outside and low level
-In this case, you will want to do the exact same thing as the previous attack, except this time, use 8 dragons and add 4 hogs to your attack. Use these 4 hogs to destroy the nearest AD. Then, continue to proceed just like attacking a TH7 with centralized and high level ADs.
-TH8 with high level ADs and on the inside
-This is the hardest of the attacks, because there are so many things that can go wrong and everything that you do will have to be perfect. In other words, your placement could mean the difference between a 2 star and a 3 star. In this case, the first thing you will want to do is choose a side to attack in which your placement of dragons along that side will hit 2 of the ADs. Next, use your lightning spells on the AD farthest away from where you will place your dragons. Next, place 10 archers on one corner of the side in which you want to attack and 10 on the other. After they destroy whatever buildings are in those corners, spread 8 dragons along the side you are attacking on (assuming you have 9 dragons and one in your clan castle). After they do some damage, place one of the two remaining dragons in a position that will destroy one of the ADs, then place the other in a position that will destroy the other AD. This next part is actually important. You want to place your barbarian king in the exact spot that you placed your dragons. At this point, hopefully your dragons are halfway through the base and may be close to or at the town hall by now. The barbarian king placement is more so an insurance package in case you don't take the town hall than it is anything else. After this, you have used all of your troops and have to watch your dragons destroy and 3 star the base!
REMEMBER: -Never bunch all of your dragons together.
-With bases that are harder to destroy, bring a dragon in your clan castle.
I hope that you found this guide helpful and I wish you many successful dragon attacks in the future!
TH8 level 87